This description relates to lift devices, and, more particularly, to mobile elevating work platform systems and methods of controlling the operation of mobile elevating work platforms.
Various types of mobile elevating work platforms have a lift mechanism that can be moved in a vertical direction to bring a worker close to otherwise inaccessible locations. The lift mechanism is often mounted to a self-propelled carriage or chassis having wheels for moving the platform between work areas. In one type of mobile elevating work platforms, the lift mechanism to achieve the vertical lift is often referred to as a “scissor lift,” in which a plurality of linked, folding supports oriented in a crisscross or “X” pattern in a “scissors stack.” The upward motion is achieved by the application of a force to a set of parallel linkages, elongating the crossing pattern, and propelling the work platform vertically. With the scissors stack mounted on the carriage above the wheels, the wheels, steering configuration, and propulsion configuration are typically a standard arrangement of axles, wheels, linkage arms, and motors or drives. Such convention steering limits the motion of the mobile work platform. For example, a turn radius is limited and the ability to crab the platform in a direction without turning it is virtually non-existent.
Scissors lift devices are most useful if they are self-propelled. Current scissor lift designs have many of the propelling features mounted under the scissors lift assembly. A hydraulic system, electrical system including batteries, and a control system are also typically mounted on the carriage below the scissors lift assembly. Additionally, axles, steering and transmission components are also mounted on the carriage under the scissors lift assembly. Many systems of the scissors lift device are controlled manually or by interlocks that prevent operation of a feature when a condition is met.